An organic EL device is a spontaneous light emitting device which utilizes the principle that a fluorescent substance emits light by energy of recombination of holes injected from an anode and electrons injected from a cathode when an electric field is applied. Since an organic EL device of the laminate type driven under a low-electric voltage was reported by C. W. Tang of Eastman Kodak Company (C. W. Tang and S. A. Vanslyke, Applied Physics Letters, Volume 51, Pages 913, 1987), many studies have been conducted on organic EL devices using organic materials as the constituting materials. Tang et al. used a laminate structure using tris(8-hydroxyquinolinol)aluminum for the light emitting layer and a triphenyldiamine derivative for the hole transporting layer. Advantages of the laminate structure are that the efficiency of hole injection into the light emitting layer can be increased, that the efficiency of forming excited particles which are formed by blocking and recombining electrons injected from the cathode can be increased, and that excited particles formed within the light emitting layer can be enclosed. As the structure of the organic EL device, a two-layered structure having a hole transporting (injecting) layer and an electron transporting and light emitting layer and a three-layered structure having a hole transporting (injecting) layer, a light emitting layer and an electron transporting (injecting) layer are well known. To increase the efficiency of recombination of injected holes and electrons in the devices of the laminate type, the structure of the device and the process for forming the device have been studied.
As the light emitting material, chelate complexes such as tris(8-quinolinolato)aluminum, coumarine derivatives, tetraphenyl-butadiene derivatives, bisstyrylarylene derivatives and oxadiazole derivatives are known. It is reported that light in the visible region ranging from blue light to red light can be obtained by using these light emitting materials, and development of a device exhibiting color images is expected (For example, Japanese Patent Application Laid-Open Nos. Heisei 8(1996)-239655, Heisei 7(1995)-138561 and Heisei 3(1991)-200889).
A device using a phenylanthracene derivative as the light emitting material is disclosed in Japanese Patent Application Laid-Open No. Heisei 8(1996)-012600. Although the anthracene derivative is used as the material for emitting bluish light, a further improvement in the efficiency of light emission has been desired. On the other hand, an improvement in the stability of the thin film has been desired so that the life of the device is increased. However, heretofore known anthracene derivatives form crystals in many cases to cause fracture of the thin film, and the improvement has been desired. For example, a dinaphthylanthracene compound is disclosed in the U.S. Pat. No. 0,593,571. However, since this compound has a symmetric molecular structure in the horizontal and vertical directions, the molecules are easily arranged to form crystals during storage at high temperatures and driving at high temperatures. Japanese Patent Application Laid-Open No. Heisei 2000-273056 discloses an allylanthracene compound asymmetric in the horizontal direction. However, one of the groups as substituents to the anthracendiyl group is a simple group such as phenyl group and biphenyl group, and the crystallization cannot be prevented.